13274522654

Committed 11 Feb 2025 11:26PM UTC coverage: 91.645% (-0.007%) from 91.652%

Build # 13274522654

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Commit Message

Merge pull request #4647 from randombit/jack/internal-assert-and-mem-ops

Avoid using mem_ops.h or assert.h in public headers

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88.51

/src/lib/math/bigint/big_code.cpp

/*
* BigInt Encoding/Decoding
* (C) 1999-2010,2012,2019,2021 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/

#include <botan/bigint.h>

#include <botan/hex.h>
#include <botan/mem_ops.h>
#include <botan/internal/divide.h>
#include <botan/internal/stl_util.h>

namespace Botan {

namespace {

consteval word decimal_conversion_radix() {
   if constexpr(sizeof(word) == 8) {
      return 10000000000000000000U;
   } else {
      return 1000000000U;
   }
}

consteval size_t decimal_conversion_radix_digits() {
   if constexpr(sizeof(word) == 8) {
      return 19;
   } else {
      return 9;
   }
}

}  // namespace

std::string BigInt::to_dec_string() const {
   constexpr word conversion_radix = decimal_conversion_radix();
   constexpr size_t radix_digits = decimal_conversion_radix_digits();
   // Use the largest power of 10 that fits in a word

   // (over-)estimate of the number of digits needed; log2(10) ~ 3.3219
   const size_t digit_estimate = static_cast<size_t>(1 + (this->bits() / 3.32));

   // (over-)estimate of db such that conversion_radix^db > *this
   const size_t digit_blocks = (digit_estimate + radix_digits - 1) / radix_digits;

   BigInt value = *this;
   value.set_sign(Positive);

   // Extract groups of digits into words
   std::vector<word> digit_groups(digit_blocks);

   for(size_t i = 0; i != digit_blocks; ++i) {
      word remainder = 0;
      ct_divide_word(value, conversion_radix, value, remainder);
      digit_groups[i] = remainder;
   }

   BOTAN_ASSERT_NOMSG(value.is_zero());

   // Extract digits from the groups
   std::vector<uint8_t> digits(digit_blocks * radix_digits);

   for(size_t i = 0; i != digit_blocks; ++i) {
      word remainder = digit_groups[i];
      for(size_t j = 0; j != radix_digits; ++j) {
         // Compiler should convert div/mod by 10 into mul by magic constant
         const word digit = remainder % 10;
         remainder /= 10;
         digits[radix_digits * i + j] = static_cast<uint8_t>(digit);
      }
   }

   // remove leading zeros
   while(!digits.empty() && digits.back() == 0) {
      digits.pop_back();
   }

   BOTAN_ASSERT_NOMSG(digit_estimate >= digits.size());

   // Reverse the digits to big-endian and format to text
   std::string s;
   s.reserve(1 + digits.size());

   if(is_negative()) {
      s += "-";
   }

   // Reverse and convert to textual digits
   for(auto i = digits.rbegin(); i != digits.rend(); ++i) {
      s.push_back(*i + '0');  // assumes ASCII
   }

   if(s.empty()) {
      s += "0";
   }

   return s;
}

std::string BigInt::to_hex_string() const {
   const size_t this_bytes = this->bytes();
   std::vector<uint8_t> bits(std::max<size_t>(1, this_bytes));

   if(this_bytes > 0) {
      this->serialize_to(bits);
   }

   std::string hrep;
   if(is_negative()) {
      hrep += "-";
   }
   hrep += "0x";
   hrep += hex_encode(bits);
   return hrep;
}

/*
* Encode two BigInt, with leading 0s if needed, and concatenate
*/
secure_vector<uint8_t> BigInt::encode_fixed_length_int_pair(const BigInt& n1, const BigInt& n2, size_t bytes) {
   if(n1.is_negative() || n2.is_negative()) {
      throw Encoding_Error("encode_fixed_length_int_pair: values must be positive");
   }
   if(n1.bytes() > bytes || n2.bytes() > bytes) {
      throw Encoding_Error("encode_fixed_length_int_pair: values too large to encode properly");
   }
   secure_vector<uint8_t> output(2 * bytes);
   BufferStuffer stuffer(output);
   n1.serialize_to(stuffer.next(bytes));
   n2.serialize_to(stuffer.next(bytes));
   return output;
}

BigInt BigInt::decode(std::span<const uint8_t> buf, Base base) {
   if(base == Binary) {
      return BigInt::from_bytes(buf);
   }
   return BigInt::decode(buf.data(), buf.size(), base);
}

/*
* Decode a BigInt
*/
BigInt BigInt::decode(const uint8_t buf[], size_t length, Base base) {
   if(base == Binary) {
      return BigInt::from_bytes(std::span{buf, length});
   } else if(base == Hexadecimal) {
      BigInt r;
      secure_vector<uint8_t> binary;

      if(length % 2) {
         // Handle lack of leading 0
         const char buf0_with_leading_0[2] = {'0', static_cast<char>(buf[0])};

         binary = hex_decode_locked(buf0_with_leading_0, 2);

         if(length > 1) {
            binary += hex_decode_locked(cast_uint8_ptr_to_char(&buf[1]), length - 1, false);
         }
      } else {
         binary = hex_decode_locked(cast_uint8_ptr_to_char(buf), length, false);
      }

      r.assign_from_bytes(binary);
      return r;
   } else if(base == Decimal) {
      BigInt r;
      // This could be made faster using the same trick as to_dec_string
      for(size_t i = 0; i != length; ++i) {
         const char c = buf[i];

         if(c < '0' || c > '9') {
            throw Invalid_Argument("BigInt::decode: invalid decimal char");
         }

         const uint8_t x = c - '0';
         BOTAN_ASSERT_NOMSG(x < 10);

         r *= 10;
         r += x;
      }
      return r;
   } else {
      throw Invalid_Argument("Unknown BigInt decoding method");
   }
}

}  // namespace Botan

1	/*
2	* BigInt Encoding/Decoding
3	* (C) 1999-2010,2012,2019,2021 Jack Lloyd
4	*
5	* Botan is released under the Simplified BSD License (see license.txt)
6	*/
7
8	#include <botan/bigint.h>
9
10	#include <botan/hex.h>
11	#include <botan/mem_ops.h>
12	#include <botan/internal/divide.h>
13	#include <botan/internal/stl_util.h>
14
15	namespace Botan {
16
17	namespace {
18
19	consteval word decimal_conversion_radix() {
20	if constexpr(sizeof(word) == 8) {
21	return 10000000000000000000U;
22	} else {
23	return 1000000000U;
24	}
25	}
26
27	consteval size_t decimal_conversion_radix_digits() {
28	if constexpr(sizeof(word) == 8) {
29	return 19;
30	} else {
31	return 9;
32	}
33	}
34
35	} // namespace
36
37	std::string BigInt::to_dec_string() const {	57✔
38	constexpr word conversion_radix = decimal_conversion_radix();	57✔
39	constexpr size_t radix_digits = decimal_conversion_radix_digits();	57✔
40	// Use the largest power of 10 that fits in a word
41
42	// (over-)estimate of the number of digits needed; log2(10) ~ 3.3219
43	const size_t digit_estimate = static_cast<size_t>(1 + (this->bits() / 3.32));	57✔
44
45	// (over-)estimate of db such that conversion_radix^db > *this
46	const size_t digit_blocks = (digit_estimate + radix_digits - 1) / radix_digits;	57✔
47
48	BigInt value = *this;	57✔
49	value.set_sign(Positive);	57✔
50
51	// Extract groups of digits into words
52	std::vector<word> digit_groups(digit_blocks);	57✔
53
54	for(size_t i = 0; i != digit_blocks; ++i) {	125✔
55	word remainder = 0;	68✔
56	ct_divide_word(value, conversion_radix, value, remainder);	68✔
57	digit_groups[i] = remainder;	68✔
58	}
59
60	BOTAN_ASSERT_NOMSG(value.is_zero());	114✔
61
62	// Extract digits from the groups
63	std::vector<uint8_t> digits(digit_blocks * radix_digits);	57✔
64
65	for(size_t i = 0; i != digit_blocks; ++i) {	125✔
66	word remainder = digit_groups[i];	68✔
67	for(size_t j = 0; j != radix_digits; ++j) {	1,360✔
68	// Compiler should convert div/mod by 10 into mul by magic constant
69	const word digit = remainder % 10;	1,292✔
70	remainder /= 10;	1,292✔
71	digits[radix_digits * i + j] = static_cast<uint8_t>(digit);	1,292✔
72	}
73	}
74
75	// remove leading zeros
76	while(!digits.empty() && digits.back() == 0) {	926✔
77	digits.pop_back();	869✔
78	}
79
80	BOTAN_ASSERT_NOMSG(digit_estimate >= digits.size());	57✔
81
82	// Reverse the digits to big-endian and format to text
83	std::string s;	57✔
84	s.reserve(1 + digits.size());	57✔
85
86	if(is_negative()) {	57✔
87	s += "-";	5✔
88	}
89
90	// Reverse and convert to textual digits
91	for(auto i = digits.rbegin(); i != digits.rend(); ++i) {	480✔
92	s.push_back(*i + '0'); // assumes ASCII	423✔
93	}
94
95	if(s.empty()) {	57✔
96	s += "0";	6✔
97	}
98
99	return s;	114✔
100	}	114✔
101
102	std::string BigInt::to_hex_string() const {	84✔
103	const size_t this_bytes = this->bytes();	84✔
104	std::vector<uint8_t> bits(std::max<size_t>(1, this_bytes));	141✔
105
106	if(this_bytes > 0) {	84✔
107	this->serialize_to(bits);	82✔
108	}
109
110	std::string hrep;	84✔
111	if(is_negative()) {	84✔
112	hrep += "-";	5✔
113	}
114	hrep += "0x";	84✔
115	hrep += hex_encode(bits);	168✔
116	return hrep;	84✔
117	}	84✔
118
119	/*
120	* Encode two BigInt, with leading 0s if needed, and concatenate
121	*/
122	secure_vector<uint8_t> BigInt::encode_fixed_length_int_pair(const BigInt& n1, const BigInt& n2, size_t bytes) {	96✔
123	if(n1.is_negative() \|\| n2.is_negative()) {	96✔
124	throw Encoding_Error("encode_fixed_length_int_pair: values must be positive");	×
125	}
126	if(n1.bytes() > bytes \|\| n2.bytes() > bytes) {	96✔
127	throw Encoding_Error("encode_fixed_length_int_pair: values too large to encode properly");	×
128	}
129	secure_vector<uint8_t> output(2 * bytes);	96✔
130	BufferStuffer stuffer(output);	96✔
131	n1.serialize_to(stuffer.next(bytes));	96✔
132	n2.serialize_to(stuffer.next(bytes));	96✔
133	return output;	96✔
134	}	×
135
136	BigInt BigInt::decode(std::span<const uint8_t> buf, Base base) {	×
137	if(base == Binary) {	×
138	return BigInt::from_bytes(buf);	×
139	}
140	return BigInt::decode(buf.data(), buf.size(), base);	×
141	}
142
143	/*
144	* Decode a BigInt
145	*/
146	BigInt BigInt::decode(const uint8_t buf[], size_t length, Base base) {	46,604✔
147	if(base == Binary) {	46,604✔
148	return BigInt::from_bytes(std::span{buf, length});	×
149	} else if(base == Hexadecimal) {	46,604✔
150	BigInt r;	42,042✔
151	secure_vector<uint8_t> binary;	42,042✔
152
153	if(length % 2) {	42,042✔
154	// Handle lack of leading 0
155	const char buf0_with_leading_0[2] = {'0', static_cast<char>(buf[0])};	3,906✔
156
157	binary = hex_decode_locked(buf0_with_leading_0, 2);	7,812✔
158
159	if(length > 1) {	3,906✔
160	binary += hex_decode_locked(cast_uint8_ptr_to_char(&buf[1]), length - 1, false);	6,092✔
161	}
162	} else {
163	binary = hex_decode_locked(cast_uint8_ptr_to_char(buf), length, false);	76,272✔
164	}
165
166	r.assign_from_bytes(binary);	42,042✔
167	return r;	42,042✔
168	} else if(base == Decimal) {	46,604✔
169	BigInt r;	4,562✔
170	// This could be made faster using the same trick as to_dec_string
171	for(size_t i = 0; i != length; ++i) {	383,604✔
172	const char c = buf[i];	379,042✔
173
174	if(c < '0' \|\| c > '9') {	379,042✔
175	throw Invalid_Argument("BigInt::decode: invalid decimal char");	×
176	}
177
178	const uint8_t x = c - '0';	379,042✔
179	BOTAN_ASSERT_NOMSG(x < 10);	379,042✔
180
181	r *= 10;	379,042✔
182	r += x;	379,042✔
183	}
184	return r;	4,562✔
185	} else {	4,562✔
186	throw Invalid_Argument("Unknown BigInt decoding method");	×
187	}
188	}
189
190	} // namespace Botan

randombit / botan / 13274522654

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